232 ■ ECHINODERMATA— PELMATOZOA phylum iv 



five minute iiifrabasals coalesced with the top stem-joint, which is frequently 

 widened and those below it not usually so. Column more or less pentagonal, 

 with the angles directed interradially. Lias to Lower Cretaceous ; Europe. 



Guettardicrinus d'Orb. Differs from Apiocrinus only in having strong 

 interbrachial plates between the lower brachials, and the consequent incor- 

 poration in the cup of a greater number of secundibrachs. Upper Jurassic ; 

 Europe. This and the two preceding genera shade into one another Avithout 

 any sharp differentiation. 



Dadocrinus Meyer. Calyx conical, of small size. Column sharply 

 pentagonal proximally, becoming round below, without cirri ; proximal 

 columnal much smaller than the calyx. Primibrachs sometimes more or less 

 connected by small interbrachials. Arms branching once. Trias ; Europe. 



Holocrinus Jaekel. Trias ; Germany. 



Jchrochordocrinus Trautschold (Cyclocrinus d'Ovh., no7i Eichw.; Mespilocrinus 

 Quenst., non Koninck). Jura and Lower Cretaceous ; Europe. Columnals 

 only are known. 



Proisocrimos A. H. Clark. Rudimentary cirri on proximal portion of the 

 column ; proximal columnals with crenulate edges ; division series very 

 broad, in lateral contact. Eecent ; Philippines, 940 fathoms. 



Carpeiiterocrmus A. H. Clark. No trace of cirri ; proximal columnals with 

 smooth edges ; division series narrow, exposing large perisomic areas. 

 Recent ; southern Japan, 565 fathoms. 



Family 4. Pentacrinidae Gray (emend.). 



Column either very long, pentagovcd or sidipent agonal, without any terminal plate, 

 and cirriferous; or represented by a single plate, also usually cirriferoiis ; in very 

 young stages similar to the stem of Bhizocrinus, but later discarded; the portion 

 retained in the adult of sessile forms is composed of columnals which have the upper 

 and lower faces ornamented with a more or less complex quinquelobate figure. Calyx 

 small, howl- or plinth-shaped, with a dicyclic base, at least in the young, but the 

 infrahasals either rudimentary or completely resorbed in the adult state; and the 

 basals may be also resorbed and metamorphosed into a curious rosette-shaped plate 

 lying entirely within the calyx. Infrahasals {where observed) three or five ; basals 

 five; radials five (one, the left posterior, sometimes much smaller than the others). 

 Primibrachs, or costals, one to eight (usually tivo). Tegmen flexible, studded with 

 small irregular calcareous particles or delicate plates which may be quite invisible to 

 the naked eye, or may form a solid covering. Arms pinnulate ; strong, from five 

 simple, to two hundred and fifty or more ultimate branches. Trias to Recent. 



Section A. Pentacrinids Gray (emend.). 

 Column persistent throughout life. 



Pentacrimis Blumenb. (Extracrinus Austin ; Polycerus Fischer pars ; ? Chlado- 

 crinus Agassiz) (Fig. 337). IBB well developed. BB usually prolonged 

 over the proximal columnals. There are rarely more than two IBr, not bearing 

 pinnules. Arms heterotomous, with two to four rami, branching only toward 

 the inside of the dichotom, into large subordinate pinnulate ramules which 

 rise to the height of the main rami, until the final divisions are all about the 

 same size ; these divisions are very numerous, in mature specimens as many 

 as forty oi- fifty to the ray. Column more or less pentangular ; the angles 



